It's not that they're bad, just that you probably won't get much for them if you try and sell, and they'll be more use to you if you ever need a spare video card or you have to throw together a makeshift gaming rig for some reason.

Meh, they can go for about $30 to $40 nowadays. If you have back up cards already, then take them to the local flea market and see what happens.
If you dont then they are a good for back ups. You wouldn't need two though.